Thursday, August 7, 2014

Few California botanists with huge collector experience

Herbarium specimens are important units of biodiversity documentation.  Gathering herbarium specimens consumes the botanist’s time:  large plant presses are heavy, gathering material in the field can be arduous; gathered material requires organizing; blotters need changing; record keeping requires effort; dried material needs to be sorted and stored; material is field id’d;  some specimens often require hours of study to label; labels require data-basing and printing; photos add to processing requirements.  All of this adds up to limit the number of specimens a field botanist can be reasonably be expected to gather(1).

Perhaps 20% o the world flora is undescribed.   For California, my estimate is that that proportion is about 10%.  Herbaria are known to contain specimens of unknown species(2); specimens are often not equally distributed within geographic regions(3).    Description of new species generally requires a minimum number of diagnostic specimens(4).  Even though we have ~2 million vascular specimens records on-line for California, we need more.

Collector prowess develops over several decades of field activity, and is a direct function of the number of encounters a field botanist enjoys with a particular taxonomic group.    In this post, I identify that the number of botanists whom develop extensive prowess with the California flora are very few individuals, and suggest that mechanisms that keep field botanists active will be required to fully document the endemic-rich California flora.

How many plants does a collector see in a lifetime?  Data from the Consortium of California Herbaria (see the figure) suggest that, as experience increases (measured by collection number), the number of encounters decreases in rapid curvilinear fashion.  In these data, very few specimens are contributed by collectors with collection numbers >10,000 (assuming that collection number and prowess/experience are directly related).

The significant feature I want to emphasize here is this:  if detection of rare or unusual species requires extensive experience with a flora, then very few botanists have gained extensive experience with a flora as rich as the California flora.  This pattern is exactly suggested by Bebber et al. “Big hitting collectors make massive and disproportionate contribution to the discovery of plant species”(5)

A larger fraction of individual botanists exhibit some or moderate experience, but are they as probable to gather specimens of novelties?  For California, there are but a handful – several dozen – botanists whom collection numbers exceed ~20,000.    Going forward, mechanisms that allow botanists to gain field extensive experience will be required to document the last of our endemic flora.

1.  Whitfield, J.  Nature 484:436-438.  2012.
2.  Bebber et. al.  Proc. National Acad. Sci. USA 107(51):22169-22171.  2010.
3.  Taylor, D.W.  Phytoneuron 2014-53:1-6.  2014.
4.  Shevock, JR; Taylor, DW.  pp. 91-98: Conservation & Management of Rare & Endangered Plants, T.S.        Elias (Ed.).  1987.

5.  Bebber et. al.  Proc. Royal Soc. B:279, 2269-2274.  2012.

A set of 30 random numbers up to 55,000 was selected, and those numbers queried in the CCH database for number of specimen records.  The number of collectors of those records could not be directly determined because of inconsistent collector names (combinations of collector initials, full names, abbreviations, and collections by committees).   However, the the number of specimens is likely to be a close proxy for the number of collectors.